Spool insulator



June 16, 1942. L. E. JOHNSON SPOOL INSULATOR Filed July 24, 1940 leuJb'aE Guam;

Patented June 16, 1942 UNlTED STATES PATENT OFFICE SPOOL INSULATOR Lewis E. Johnson, Arlington, Tex., assignor to Porcelain Products, Inc., Findlay, Ohio, a corporation of Delaware 6 Claims.

This invention relates to spool insulators by which cables carrying electric current may be supported from a rack, pole or the like.

It has long been common practice to use porcelain knobs or spools as supports for electric cables. Such spools are made from single masses of plastic material having suitable dielectric properties. The spools ordinarily provide a large peripheral groove in which the current carrying cable is held. When the spool is mounted with its axis horizontal this peripheral groove forms a stirrup or saddle upon which the line Wire rests. If the spool or knob is mounted with its axis vertical as on a vertical pin of a rack, cross arm or the like, then the current carrying cable is held against the groove and at one side of the spool.

In either position the cable is attached to the spool by means of a length of tie wire or the like having its ends wrapped around the running part of the cable and its mid-portion passing through the groove on the opposite side from the cable.

I have discovered that material improvement can be obtained in the convenience of these devices and in the permanency with which the line wire may be held by giving the spools modified forms contributing to their efficiency. Broadly speaking, the invention consists in providing a tangential groove to receive the line wire or cable so that it will have a more extended contact with the supporting surfaces of the spool. Incidentally, the longitudinal axis of the cable will be brought within the outer extent of the spool thus providing a more compact arrangement and improving the position of the center of gravity of the mass being supported.

By modifying the form of this spool in accordance with the following description, a lip or rib is provided for forming a stirrup for the cable and preventing any tendency of the latter to slide out of the peripheral groove.

Other objects of my invention will be apparent from the description of the preferred form of my invention as illustrated in the accompanying drawing in which Fig. 1 is a front elevation of the spool partly in section and Fig. 2 is a side elevation of the same.

As illustrating the preferred form which my invention may take I have shown a spool insulator denoted generally by the numeral 3 to consist of a single piece of molded plastic material having suitable electrical insulating properties. This material may be either thermoplastic or ceramic such as porcelain. It is intended that the spool be given its final form by heat or firing and that the surface will be rendered smooth by glazing or the like.

The spool is generally cylindrical with an axial opening 4 by which it may be suitably mounted upon a rack, pin or other support. The usual round base 5 is provided with the central annular projection G and intermediate depressed groove 1.

The opposite or top portion 8 of the insulator slopes down or away from the central opening 4. This portion also has two ribs 9 and 10 providing an intermediate groove 1! by which the leakage path is increased.

Intermediate the base 5 and the rib in there is a peripherally grooved portion l2. This peripheral groove is circular in cross-section on a radius indicated in Fig. 1 by the letter R. It will be noted that this radius extends to a center outside of the limit of the base 5 and top portion 8. Thus the groove may be said to be a flaring one. This arrangement of the peripheral groove is that customarily used in devices of this type.

I have modified the groove I2 by providing a tangential groove l3. This groove l3 exends for perhaps degrees of the circumference of the spool and undercuts or subtends the groove l2 to a material degree. The inner wall of the groove I3 is straight and forms an extended seat for the line wire or cable.

As shown at the left of Fig. 1 the tangential groove [3 has a cross-sectional radius r, the center of which is within the overhanging extremities of the base 5 and the rib It). It follows that the tangential groove I3 is, therefore, more than degrees in lateral extent.

Either the rib l0 or the base 5 may be provided with means for retaining the line wire within the tangential groove l3. For purposes of illustration I have shown this means as forming a part of the base 5. Here the material in the base portion 5 extends upwardly a slight distance above the lower limit of the groove l3. There is thus formed a lip or rib M which projects into the tangential groove.

It will be seen that this novel improvement in spool insulators consists in modifying the conventional peripheral groove to provide a tangential groove which may extend as a chord of the insulator for as much as 1 d re s. This provides a fiat extended contact which insures a firm grip upon a cable without it being bent partly around the spool by the tie wire. Also when the spool is mounted on a vertical axis the inwardly projecting lip l4 retains the cable against accidentally sliding out of the flaring groove l2 until such time as the tie wire can be secured. This lip [4 may extend either from the base 5 or the rib I0. It will also be apparent that in the event that the cable has a diameter equal to that of the tangential groove l3, then the lip will form a detent for clampin the cable against the opposite portion of the spool and at a point outwardly from the axis of the cable as represented by the center from which the radius 1 extends.

While I have illustrated the preferred form of my invention for purposes of example, it will be understood that the scope of the invention is limited only by the following claims.

What I claim is:

1. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, and a tangentially grooved portion intersecting said peripheral groove.

2. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, and a tangentially grooved portion intersecting said peripheral groove and having an angular subtending extent of approximately 120 degrees.

3. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, and a tangentially grooved portion intersecting said peripheral groove said tangential groove having a circular cross-section with its center inwardly of the base portion.

4. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, said groove being part-circular in cross-section on a center outwardly of the base portion, and a tangentially grooved portion intersecting said peripheral groove and having a circular cross-section with its center inwardly of the base portion.

5. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, a tangentially grooved portion intersecting said peripheral groove and a lip projecting into said tangential groove.

6. In a spool insulator formed of a single mass of insulating material generally cylindrical in form with an axial opening, a circular base portion, and a circular top portion, the insulator having a peripheral groove between said base and top portions, a tangentially grooved portion intersecting said peripheral groove and a lip projecting vertically from the base portion into said tangential groove.

LEWIS E. JOHNSON. 

